Afternoon all/
Hope this is the right place and I've broken no forum rules, I'm completely new to this.
I've upgraded from OMV 4 to 5 this afternoon after upgrading from 3 to 4 a couple of days ago and then realising that 4 was eol'd as well!
My hardware is an HP Micro server N54L AMD turion II I bought used off a colleague for £40 or so.
It sits there running a raid of 4 x 1TB HDDs holding the local copy of the family photos and some tv and films accessed by the Plex media server plugin.
I'm ssh'd from Linux Mint running on a ten year old SFF Acer PC!!
I followed the notes in the OMV forum "OMV 5.0 - finally out! 
page #38"
Here's the edited history of how this afternoon went, maybe it helps somebody;
452 wget -O - https://github.com/OpenMediaVa…pt/raw/master/upgrade4to5 | sudo bash
This script failed to finish on my machine.
453 reboot
471 apt-get purge openmediavault-omvextrasorg resolvconf
Still broken, apt-get purge recommended to run the following apt --fix-broken command.
472 apt --fix-broken install
Said N to installing new versions.
It fixed loads of stuff probably from previous upgrades and attempts and me thrashing around in the dark.
473 wget -O - https://github.com/OpenMediaVa…pt/raw/master/upgrade4to5 | sudo bash
This second attempt got a lot further than #452 but still failed at the very end but I thought a reboot was worth it.
474 reboot
475 apt --fix-broken install
This did a few more fixes and looked hopeful so tried continuing;
476 apt-get purge openmediavault-omvextrasorg resolvconf
Didn't complete fully so tried this again;
477 apt --fix-broken install
And it fixed some more.
478 apt-get purge openmediavault-omvextrasorg
Completed without error.
Ran the next command on the forum page.
479 wget -O - https://github.com/OpenMediaVa…ckages/raw/master/install | bash
Completed without error.
480 apt-get update
Completed without error
481 apt-get dist-upgrade
Completed without error but whinged about a load of unused packages and suggested running;
482 apt autoremove
Which removed them and completed without error
483 reboot
Logged in from web ok, cleared browsr cache and reported version omv 5.
Did a couple of things and then got the dreaded 502 nginx message in the browser instead of the login screen.
More googl-ing
484 omv-firstaid
Didn't fix anything
487 omv-mkconf nginx
Mis-direction, omv-mkconf doesn't exist in omv 5 apparently
490 omv-salt deploy run nginx
Didn't fix the web login
495 dpkg -l | grep openm
ii openmediavault 5.5.12-1 all openmediavault - The open network attached storage solution
ii openmediavault-keyring 1.0 all GnuPG archive keys of the OpenMediaVault archive
ii openmediavault-omvextrasorg 5.4.2 all OMV-Extras.org Package Repositories for OpenMediaVault
ii openmediavault-plexmediaserver 3.8.2 all OpenMediaVault Plex Media Server plugin
496 apt --fix-broken install
Reading package lists... Done
Building dependency tree
Reading state information... Done
0 upgraded, 0 newly installed, 0 to remove and 1 not upgraded.
So nothing to fix, hmm, what now? more googling.
497 omv-firstaid
Still didn't help.
498 omv-salt deploy run phpfpm
FIXED the web login and plex survived the upgrade and is still up and running - bonus.
So got there in the end, thanks everyone for all the hard work and info..